Safety device to prevent film burning



Jan, 29, 1935. I M. H. FRITZ 1,989,310

SAFETY DEVICE TO PREVENT FILM BURNING Filed March 14, 1932 bwentar Maxif.

, Aflorneys Patented Jan. 29, 1935 UNITED STATES;

PATENT OFFICE SAFETY DEVICE TO PREVENT FILM BURNING Max 11. Fritz,Berlin,

,asslgnortothe Application March 14, 1932, Serial No. 598,858 In GermanyMarch 12, 1931 3 Claims. (01. aa-i'n My invention relates to safetydevices to prevent film burning.

The object of the present invention is an apparatus which is influencedby the upper film loop, increased if the film band breaks, the loopmoving an electric contact, operating a lever, the moving device ofwhich will be released by meansof a band attached to one end of thelever and holding it in neutral position, which band will be touched bythe film loop.

This new apparatus obviates all disadvantages of the devices known untilnow which require too much force in releasing the contacts. Yet, to

prevent any fire, it is necessary that in case of breaking of the filmband the electric contacts are released in a period which is very smallin comparison with the moving speed of the film band. Therefore allthose devices are not useful with which relatively big masses are to beoperated, the inertia of which must be overcome.

Fire preventing devices with which-if the upper film loop is increased-alever and electromagnets are released, to close the fire safety valveare known as well as mercury rocking switches operating further safetydevices. But the present invention consists in avoiding moving ofheavier masses by nieans of using a lever held in neutral position by aband attached to one end of the lever and touched by the increasing filmband.

In the drawing forming a part of this specification, is shown a safetydevice in accordance with my invention.

In detail, the invention comprises a film loop 1 increasingautomatically in case of breaking of the film band or if locked inwindow 2 or at any other disturbance, to be pressed against the bal-.

ancing band 3 which is attached to balancing lever 4 and to adjustablearm 20, the band being of any material or metal or a thread or wire orthe like. At the slightest pressure the highly sensitive balancing lever4 supported by an axle is moved out of its position and raised againstthe contact piece 5. The contact piece 5 and the balancing lever 4 arelying in an electric circuit, so that in closin'gthe circuit currentpasses through the magnet 6, knocking the magnet core against the doubleacting lever 8. Now the lever 8, supported by an axle, is lifted out ofits neutral position, hook of the fire safety valve, slides out ofsupporting device 9, while the fire safety valves 12 attached to thesupporting device by means of a string 11 or the like close theprojection and sight openings 13. Furthermore it ispossibletousethelefts'ideofthedoubleaeting lever 8 to operate a firesafety valve between the lantern and the projection window. At the sametime arm 14 releases lever 16 supported by axle 15, so that nose 17slides off lever 14 and that mercury switch tubes l8, 19 attached tolever 16 indifferent positions are switched on or off. The lever 18 willbe stopped at 23 and 24. The number of the mercury switch tubes may bechosen as to the necessary functions. For instance it may be possible toswitch off the projection lantern, the driving motor of the projectorand at talkies the talkies apparatus, and switch on the lights of thetheatre.

After the disturbance of the film moving is finished, the device isswitched back into its normal position by turning button 19. This button19 is connected to lever 16, and raising it against the action of spring22, permits the spring 21 to act and draw the lever 8 into its neutralposition, as shown in the drawing. -Now, the fire safety valve 12 may belifted and supporting device 9 attached to hook 10.

I claim:

1. In a safety device for preventing film burning in cinematographicprojectors, a pivoted lever, a flexible member stretched between a fixedsupport and one end of said lever, and normally out of contact with themoving film, and electric means adapted to be energized when the otherend of the lever contacts with a stationary contact member, wheneversaid flexible member is touched by a loop of film, as a result of anydisturbance in the movement of said film travelling through theprojector.

2. In a safety device for motion picture projectors, a pivoted lever, aflexible member stretched between a stationary support and one end ofthe lever and normally out of contact with afilm moving in theprojector, to hold said lever in a given position, an electric contactadapted to be engaged by the free end of the lever whenever acinematographic film travelling through the projector touches theflexible member, and an electric circuit including a source and anelectro-magnet, said circuit being closed through the lever whenever ittouches the electric contact, whereby the electro-magnet is adapted totrip mechanism efifectuating the energization of safety devices actuatedelectrically.- I

3. A safety device for cinematographic projectors, comprising incombination with such a projector and the film travelling therethrough,a pivoted lever, a flexible member attached to a fixed support and" oneend of the lever and normally out of contact with the moving film, saidflexible member being disposed adjacent one loop of the film, anelectric circuit including a source. an electro-magnet and contactingmeans adapted to close said circuit through the lever when the 5 same iscaused to engage its free end with the contacting means, as a. result ofdisturbances in the film movement causing the loop to act on theflexible member, and auxiliary electric circuits controlling meanscomprising a. tripping member acted upon by the electro-magnet andincluding a plurality of mercury switches adapted to control suitablesafety devices, said switches being operated by the tripping member.

MAX H. FRITZ.

